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cuserid(3) [osf1 man page]

cuserid(3)						     Library Functions Manual							cuserid(3)

NAME
cuserid - Gets the alphanumeric username associated with the current process LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <stdio.h> char *cuserid( char *s); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: cuserid(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Points to the character array into which the cuserid() function copies the string representing the username. This array must contain at least L_cuserid bytes. L_cuserid is a constant defined in the stdio.h header file, and has a value greater than 0 (zero). If you specify a null pointer for s, the character string is stored into an internal thread-specific buffer, the address of which is returned. DESCRIPTION
The cuserid() function generates a character string representing the real or effective username of the owner of the current process. NOTES
If the s parameter is a null pointer, the character string is stored into an internal thread-specific buffer, the address of which is returned. Subsequent calls to the cuserid() function from the same thread overwrite the contents of the internal buffer. The cuserid() function is scheduled to be withdrawn from a future version of the X/Open CAE Specification. RETURN VALUES
If the s parameter is not a null pointer, the cuserid() function returns the character string in the array pointed to by s. If the user- name cannot be found, an empty string is returned. If the s parameter is a null pointer, the character string is stored into an internal thread-specific buffer, the address of which is returned. If the username cannot be found, a null pointer is returned. RELATED INFORMATION
Functions: getlogin(2), getpwent(3) Standards: standards(5) delim off cuserid(3)

Check Out this Related Man Page

GETLOGIN(3)						     Linux Programmer's Manual						       GETLOGIN(3)

NAME
getlogin, cuserid - get user name SYNOPSIS
#include <unistd.h> char *getlogin(void); #include <stdio.h> char *cuserid(char *string); DESCRIPTION
getlogin returns a pointer to a string containing the name of the user logged in on the controlling terminal of the process, or a null pointer if this information cannot be determined. The string is statically allocated and might be overwritten on subsequent calls to this function or to cuserid. cuserid returns a pointer to a string containing a user name associated with the effective user ID of the process. If string is not a null pointer, it should be an array that can hold at least L_cuserid characters; the string is returned in this array. Otherwise, a pointer to a string in a static area is returned. This string is statically allocated and might be overwritten on subsequent calls to this function or to getlogin. The macro L_cuserid is an integer constant that indicates how long an array you might need to store a user name. L_cuserid is declared in stdio.h. These functions let your program identify positively the user who is running (cuserid) or the user who logged in this session (getlogin). (These can differ when setuid programs are involved.) For most purposes, it is more useful to use the environment variable LOGNAME to find out who the user is. This is more flexible precisely because the user can set LOGNAME arbitrarily. ERRORS
ENOMEM Insufficient memory to allocate passwd structure. FILES
/etc/passwd password database file /var/run/utmp (traditionally /etc/utmp; some libc versions used /var/adm/utmp) CONFORMING TO
POSIX.1. System V has a cuserid function which uses the real user ID rather than the effective user ID. The cuserid function was included in the 1988 version of POSIX, but removed from the 1990 version. BUGS
Unfortunately, it is often rather easy to fool getlogin(). Sometimes it does not work at all, because some program messed up the utmp file. Often, it gives only the first 8 characters of the login name. The user currently logged in on the controlling tty of our program need not be the user who started it. Avoid getlogin() for security-related purposes. Nobody knows precisely what cuserid() does - avoid it in portable programs - avoid it altogether - use getpwuid(geteuid()) instead, if that is what you meant. DO NOT USE cuserid(). SEE ALSO
geteuid(2), getuid(2) Linux 1.2.13 1995-09-03 GETLOGIN(3)
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